Conventionally, there is suggested a construction machine of which a part of a drive mechanism is motorized. Such a construction machine is equipped with an electric motor as a power source of a turning mechanism for rotating an upper turning body in order to accelerate (drive) the turning mechanism by a power running operation of the electric motor and, when decelerating (braking) the turning mechanism, performing a regenerative operation to charge the generated electric power to a battery (for example, refer to Patent Document 1). Moreover, the construction machine disclosed in Patent Document 1 is equipped with a hydraulic pump to hydraulically drive a drive mechanism other than a turning mechanism, and a generator is connected to an engine for driving the hydraulic pump via a speed-up gear to use electric power acquired by generation for charging a battery and driving the electric motor of the turning mechanism.
Patent Document 1: Japanese Laid-Open Patent Application No. 2004-036303